A Couple Questions for before my Trip

Hey Everyone! So quick summary, I’ll be landing in Japan sept 13 and flying out October 1st. I’ll be visiting Tokyo, Hiroshima, Osaka, Nara, Kyoto and Hakone.

I will probably be getting an online IC card but I do wonder is there any downside if I were to just use cash or card there to pay for my fair?

When it comes to spending, is card or cash preferred? I do know there will be stuff that is cash only and it’s good to keep some for that.

I have all my hostels booked but yet to pay. Since booking the yen has gone up, making the total around 50 dollars (cad) more then when I first booked. Honestly not a big deal but did get me wondering if it makes more sense to pay now or just wait the month and pay in the beginning of September like originally planned?

Last question is site specific. I am seeing that the Tone river firework festival is being held on Sept 14th. I see the main site but am curious if anyhow who has gone knows of any other good spots that one can view them at?

That is all I have to ask! Of course I am open to any tip or suggestions for my trip!

Thanks!